feat(ast): add species base to template declarations

Added optional species_base field to Template struct enabling
template-species inheritance syntax: `template Name: Species { ... }`.
Updated LALRPOP grammar and all Template construction sites.

src/syntax/parser.lalrpop

@@ -169,7 +169,7 @@ UsesScheduleClause: Vec<String> = {
 // ===== Template =====
 
 Template: Template = {
-    "template" <name:Ident> <strict:"strict"?> "{" <body:TemplateBodyItem*> "}" => {
+    "template" <name:Ident> <species_base:(":" <Ident>)?> <strict:"strict"?> "{" <body:TemplateBodyItem*> "}" => {
         let mut fields = Vec::new();
         let mut includes = Vec::new();
         let mut uses_behaviors = None;
@@ -186,6 +186,7 @@ Template: Template = {
 
         Template {
             name,
+            species_base,
             fields,
             strict: strict.is_some(),
             includes,